The present invention relates generally to radar, and more particularly, to radar systems having jamming suppression features.
While radars can be highly effective in ascertaining the location of remote objects, the accuracy of radars can be greatly reduced in the case where a radar is jammed. As is well known to one of ordinary skill in the art, radars generally transmit energy at predetermined frequencies and receive energy reflected back from one or more targets. As is also well known, a radar system may be jammed by a remote signal source that intentionally creates the appearance of a false target or by transmitting large amounts of energy intended to saturate a radar receiver.
Many attempts have been made to suppress jamming of radars. In one known technique, nulls are formed in the radiation pattern in positions corresponding to the location of the jamming or interfering source. However, when it is desired to form a null in a sum beam, and in a difference beam, conventional radar systems require so-called subarray control modules to provide additional degrees of freedom. More particularly, since a transmit/control module typically controls only one channel (sum or difference) at a time, the subarray control modules are required to place nulls in the difference pattern at locations that correspond to the nulls in the sum pattern.
Such subarray control modules have several significant disadvantages. For example, each module is subject to hardware failures that can significantly degrade radar performance. In addition, the modules must amplify large signals without introducing non-linearities into the system and thus require unique and costly components.
It would, therefore, be desirable to provide a radar system that enhances the anti-jamming ability of a monopulse radar system by introducing nulls in sum and difference patterns without the need for subarray control modules.
The present invention provides a monopulse radar system that suppresses jamming of the radar. In an exemplary embodiment, a radar system includes a null processor that provides a null in the sum beam at a location that corresponds to an identified jamming source. The null processor then forms a difference pattern from a product of the sum pattern and the sin of the angle error, i.e., sum*sin(x). The resultant difference pattern has a null in a location that corresponds to the jammer null in the sum beam. Thus, both the sum and difference beams of the system have nulls in the same location.
Forming the difference pattern from the sum pattern and the sin of the angle error eliminates the need for subarray control modules to place nulls in the difference pattern that correspond to the nulls in the sum pattern. Thus, the radar system provides advanced jamming suppression features while reducing the cost and complexity as compared with conventional radar systems having subarray control modules to provide additional degrees of freedom for the difference beam.